Method and apparatus for forming a metallic container

ABSTRACT

A method of forming a metallic container includes the steps of providing body and lid portions, placing the body and lid portions together, keeping portions of the body and lid portions in contact with one another, and reciprocally rotating the lid portion with respect to the body portion, thereby generating frictional heat and forming a friction weld therebetween. An apparatus for attaching the lid and body portions of a metallic container includes a base to support the body, a support assembly to support a flange of the body, and a sonitrode for contacting a flange of the lid, wherein the flanges of the lid and body are held together between the support assembly and the sonitrode. A motor reciprocally rotates the sonitrode relative to the support assembly, thereby moving the flanges relative one another to generate frictional heat and create a friction weld therebetween.

This application is a continuation of application Ser. No. 11/313,111filed Dec. 20, 2005, now U.S. Pat. No. 7,748,101 which is incorporatedherein by reference.

BACKGROUND

1. Field of the Invention

The invention generally relates to a method an apparatus for attachingthe lid portion to the body portion of a metallic container,particularly a metallic food container such as an aluminum beverage can.

2. Background of the Invention

Metallic containers, particularly those intended for food products, mustbe structurally robust, be made from materials compatible with foodproducts, and generally incorporate internal coatings to make themsuitable for food contents. Generally, metallic food containers, such ascarbonated beverage cans, have a pre-formed body portion and apre-formed lid portion that is attached to the body portion after thebeverage is placed therein. The body portion is usually formed from asingle piece of suitable metallic material, such as aluminum, and isshaped by stamping, drawing, ironing, and/or other suitable metalforming process. The lid portion is formed in much the same manner. Thebody portion can be very thin after forming, and therefore, the lidportion desirably contributes to the structural rigidity for thefinished container. The lid portion can be made from a material that isrelatively harder than the body portion.

One known method of attaching the lid portion onto the body portion ofthe metallic container involves rolling or curling parallel flangeportions of the lid and the body portion onto each other to form a lipseam. This process generally provides a good seal, and does notcompromise the integrity of any coatings that may be placed on theinterior of the metallic container. A variety of coatings can be used onthe interior surfaces of the lid portion and the body portion of thecontainer, which are preferably satisfactory for food contact, toprevent corrosion of the inner surface of the metallic food containerand to prevent the metal from contaminating the taste of the food placedtherein. The coating can be any of the materials identified, forexample, in U.S. Pat. No. 5,739,215, which are hereby incorporated byreference. Typically, the body portion and the lid portion have theinner surfaces coated prior to the lid portion being attached to thebody portion. Therefore, any attachment technique must account for andaccommodate the coating.

By rolling the edges of the lid portion and the body portion onto oneanother, a tight seal is formed, and the coating is not compromised.However, this method of attachment requires extra metallic material toallow for portions to be rolled over onto one another in this manner.Additionally, typically in this process a vinyl seal or gasket can beplaced between the edges of the lid portion and the body portion beforethey are rolled onto one another. This gasket material helps insure anadequate seal.

Other techniques can be used to reduce the amount of metallic materialby directly connecting the edges by welding or soldering the edgestogether, by a process such as laser welding. This process will alsoprovide a sealed attachment, however the temperatures necessary for thistype of welding are high enough to compromise or destroy any coatingplaced on the inner surface of the body portion and the lid portion.This leaves an uncoated region immediately adjacent the area of theweld. Still other methods may use an intermediate material, with a lowermelting point, between the lid portion and the body portion, to allowthe lid portion and the body portion to be welded together, via theintermediate material, at a lower temperature.

Further, the processes discussed above, either rolling the edges of thelid portion and the body portion over onto one another, or welding theedges together require significant time to complete, thereby making themanufacture of these metallic containers more costly. The lid isgenerally attached to the body of the metallic container after thecontents of the container have been placed therein. In the case of acarbonated beverage, as soon as a seal forms between the lid and thebody of the metallic container, pressure will start to build within thecontainer. This can cause carbonated beverage to be pushed between thelid and the body as the seal is being formed, thereby compromising thequality of the seal. Also, specifically with carbonated beverages, theportion of the beverage that leaks from within the container during theprocess of attachment makes a mess within the manufacturing facility.

Therefore, there is a need for an apparatus and method of forming ametallic container that will allow for a reduction in the amount ofmaterial used while providing a sealed attachment between the lidportion and the body portion without compromising any food compatiblecoatings placed on the inner surfaces of the lid portion and the bodyportion. Furthermore, there is a need for an apparatus and method offorming a metallic container that will reduce the cycle time of priormethods used to attach the lid to the body of a metallic container.

SUMMARY

In one aspect, an apparatus for attaching a lid portion to a bodyportion of a metallic container can include a base adapted to supportthe body portion of the metallic container when placed thereon, and asupport assembly, movable relative to the base. The support assembly canhave a support surface adapted to support an outer surface of a flangeportion of the body of the metallic container. A reciprocally rotatablesonitrode can include a friction surface that can be moved linearly,generally along a longitudinal axis, relative to the support assemblybetween a retracted position, and an engaged position. When the lidportion is placed onto the body portion of the metallic container, andthe support assembly engages the outer surface of the flange portion ofthe body of the metallic container, the sonitrode can be moved to theengaged position, so that confronting portions of the lid and the bodyof the metallic container are held in contact with one another betweenthe support surface of the support assembly and the friction surface ofthe sonitrode. A motor can reciprocally rotate the sonitrode relative tothe support assembly, thereby moving the lid portion of the containerrelative to the body portion of the container. The relative movement canbe such that frictional forces generated by the reciprocal rotationalmotion can wipe out any coating materials on the contacting surfaces ofthe lid portion and body portion of the container, and can create afriction weld between the materials forming the lid and body portions ofthe container.

In another aspect, the motor can be adapted to reciprocally rotate thesonitrode at a rate of approximately twenty KHz, and the apparatusfurther includes an actuator for advancing and retracting the sonitrodebetween the engaged position and the retracted position. When thesonitrode is moved to the engaged position, the actuator can move thesonitrode downward in stages such that the sonitrode exerts an initialdownward force to hold portions of the lid and the body of the metalliccontainer in contact with one another between the support surface of thesupport assembly while the coating materials on the contacting surfacesare wiped out. The term “wiped out” is intended to connote thedestruction and/or outward displacement of the coating materials on theconfronting contacting surfaces or the lid portion and body portion ofthe container. Following the wipe out of the coating materials, thedownward force can be increased to create the friction weld between thematerials forming the lid and body portions of the container. Theactuator can provide a downward force of up to 7200 N, but mosttypically, provides a downward force of approximately 2200 N.

In still another aspect, the support assembly can include a frame and aclamshell anvil. The clamshell anvil can take the form of two halvesthat are pivotally mounted onto opposing portions of the frame. The twohalves of the pivotally mounted clamshell anvil can be pivotallymoveable between an open position and a closed position and can bebiased to the open position.

In yet another aspect, the sonitrode can be supported on a shaft havinga cammed outer surface. Portions of the pivotally mounted clamshellanvil halves can engage the cammed outer surface, such that when thesonitrode is in the retracted position, the pivotally mounted clamshellanvil halves can engage the shaft at a point where the shaft can allowthe clamshell anvil halves to pivot to the open position. When the shaftand the sonitrode begin to move downward, the cammed outer surface ofthe shaft can be used to force the clamshell anvil halves to pivot tothe closed position so that the support surface can engage the rimportion of the body of the container. The cammed outer surface of theshaft can be shaped such that the clamshell anvil halves can be forcedto pivot to the closed position prior to the sonitrode reaching theengaged position.

In still another aspect, at least one of the clamshell anvil halves caninclude a stop extending from an inner surface of the clamshell anvilhalf. The stop can be positioned vertically above the support surface,such that when the sonitrode retracts from the lid of the metalliccontainer after welding, if the lid portion sticks to the frictionsurface of the sonitrode, the stop can contact the lid portion, tothereby hold the metallic container down as the sonitrode retractsupward.

In yet another aspect, the support surface of the support assembly canhave a textured surface such that the support surface can frictionallyengage the outer surface of the rim portion of the body of the metalliccontainer to prevent sliding movement of the rim portion of the bodyrelative to the support surface. The friction surface of the sonitrodecan also have a textured surface such that the friction surface willfrictionally engage the lid portion of the metallic container to preventsliding movement of the lid relative to the friction surface. Thetextured surfaces can take a variety of forms including, withoutlimitation, a criss-crossed knurl pattern, a diamond shaped knurlpattern, a vertically aligned knurl pattern, a raised serpentine ridgepattern, sand-blasted grit surface. Some forms of the textured surfacescan result in surprisingly enhanced performance.

In still another aspect, an interior surface of the body portion and thelid portion of the metallic container can include a protective coating.When the sonitrode is moved to the engaged position, the sonitrode canexert a downward force to hold portions of the lid and the body of themetallic container in contact with one another between the supportsurface of the support assembly and the friction surface of thesonitrode. The downward force of the sonitrode and the frequency ofreciprocal rotation of the sonitrode can be such that the frictionalheat generated from the reciprocal relative motion between the lidportion and the body portion is sufficient to create a friction weldbetween the lid portion and the body portion of the metallic container,and sufficiently low not to cause break-down of the coating in the areasimmediately inwardly adjacent to the frictional weld.

In still another aspect, the friction surface of the sonitrode and thesupport surface of the support assembly can be oriented at almost anyangle down to approximately five degrees to seven degrees relative tothe longitudinal axis of the apparatus.

In another aspect, a method of forming a metallic container includes thesteps of providing a pre-formed body portion and providing a pre-formedlid portion. The body and lid portions can include angled flanges forconfronting one another, as well as the body and lid portions can alsobe coated with a coating. The method also includes the steps of placingthe lid portion onto the body portion and applying a force to keepportions of the lid portion and the body portion held in contact withone another, and reciprocally rotating the lid portion with respect tothe body portion, thereby generating frictional heat between the lidportion and the body portion such that a friction weld is formedtherebetween. The method steps may also include applying a force to keepconfronting portions of the lid portion and the body portion held incontact with one another and reciprocally rotating the lid portion withrespect to the body portion at a rate for a first predetermined amountof time to generate a sufficient amount of frictional heat therebetweento wipe the coatings away from the confronting portions. Further, themethod steps may include increasing at least one of the force appliedand the rate of reciprocal rotation for a second predetermined amount oftime after the first period has passed, to generate a second frictionalheat, larger than the frictional heat for removing the coating, suchthat a friction weld is formed between the confronting portions.

DESCRIPTION OF THE DRAWINGS

The above, as well as other advantages of the present invention willbecome readily apparent to those skilled in the art from the followingdetailed description of a preferred embodiment when considered in thelight of the accompanying drawings.

FIG. 1 is a partial sectional view of an apparatus in accordance withthe present invention, wherein a sonitrode is in the fully retractedposition.

FIG. 2 is a view similar to FIG. 1, wherein the sonitrode is movingdownward toward the engaged position.

FIG. 3 is a view similar to FIG. 1, wherein the sonitrode is in theengaged position.

FIG. 3A is a close up view of a portion of FIG. 3 as indicated by thearea labeled “3A” in FIG. 3.

FIG. 4 is a top view of the lid portion of a metallic container.

FIG. 4A is a sectional view taken along line 4A-4A of FIG. 4.

FIG. 5 is a side sectional view of the body portion of a metalliccontainer.

FIG. 5A is an enlarged view of a portion of FIG. 5 as indicated by thearea labeled “5A” in FIG. 5.

FIG. 6 is an enlarged view of a portion of FIG. 3A as indicated by thearea labeled “FIG. 6” in FIG. 3A, prior to friction welding.

FIG. 7 is a view similar to FIG. 6, shown after friction welding.

FIG. 8 is an enlarged portion of FIG. 7 as indicated by the area labeled“8” in FIG. 7.

FIG. 9 is a perspective view of a portion of the support surface whereinthe support surface has a criss-crossed knurl pattern formed thereon.

FIG. 10 is a perspective view similar to FIG. 10 wherein the frictionsurface has a diamond shaped knurl pattern formed thereon.

FIG. 11 is a perspective view of a portion of the friction surface onthe sonitrode wherein the friction surface has a vertically alignedknurl pattern formed thereon.

FIG. 12 is a perspective view of a portion of one of the frictionsurface and the support surface, wherein the surface has been gritblasted.

FIG. 13 is a perspective view of a portion of one of the frictionsurface and the support surface, wherein the surface includes a raisedserpentine ridge extending thereabout.

FIG. 14 is a sectional view taken along lines 14-14 of FIG. 13.

DESCRIPTION OF THE EMBODIMENTS

Referring to FIG. 1, an apparatus for attaching a lid portion 10 to abody portion 12 of a metallic container 14 is shown generally at 16. Theapparatus 16 is shown to include a base 18 that is adapted to supportthe body portion 12 of the metallic container 14 when placed thereon.Referring to FIGS. 5 and 5A, the body portion 12 of the metalliccontainer 14 is generally cylindrically shaped and open at one end 11.The open end 11 includes an angled flange 20 extending circumferentiallyaround the open end 11. A support assembly 22 is movable relative to thebase 18 and is shown to include a support surface 24 adapted to supportan outer surface 26 of the flange 20.

The support assembly 22 includes a frame 28 and a clamshell anvil 30.The clamshell anvil 30 includes two halves 30A, 30B that are pivotallymounted onto opposing portions of the frame 28. The two halves 30A and30B of the clamshell anvil 30 pivot between an open position shown inFIG. 1 and a closed position shown in FIG. 3. Referring to FIG. 1, inthe open position, the support surface 24 is pivoted away from theflange 20 of the body portion 12, thereby allowing the body portion 12to be loaded and unloaded from the base 18. Referring to FIGS. 3 and 3A,in the closed position, the two halves of the clamshell anvil 30 arepivoted inward such that the support surface 24 contacts and supportsthe outer surface 26 of the flange 20 of the body portion 12.

A reciprocally rotatable and vertically moveable sonitrode 32 is mountedvertically above the base 18. The sonitrode 32 includes a frictionsurface 34 and is moveable linearly, along a longitudinal axis 36,relative to the support assembly 22 between a retracted position, shownin FIG. 1, and an engaged position, shown in FIG. 3. Referring to FIG.1, in the retracted position, the sonitrode 32 is positioned verticallyabove the base 18 as well as the body portion 12 and lid portion 10 ofthe metallic container 14 situated on the base 18. Referring to FIGS. 3and 3A, after the support assembly 22 engages the outer surface 26 ofthe flange 20 of the body 12 of the metallic container 14, the sonitrode32 is moved to the engaged position, wherein the friction surface 34 ofthe sonitrode 32 contacts the lid portion 10 of the metallic container14.

Referring to FIGS. 4 and 4A, the lid portion 10 of the metalliccontainer 14 is generally disk shaped and includes an angled flange 38extending circumferentially around the disk perimeter. The angle 40 ofthe flange 20 on the body portion 12 is approximately equal to the angle40 of the flange 38 on the lid portion 10 of the metallic container 14,such that when the lid portion 10 is placed onto the body portion 12, aninner surface 42 of the flange 38 on the lid portion 10 contacts aconfronting inner surface 44 of the flange 20 on the body portion 12.The flange 38 on the lid portion 10 includes a curled lip 46 which curlsoutward such that when the lid portion 10 is placed onto the bodyportion 12, the curled lip 46 engages the distal end of the flange 20 onthe body portion 12. The angled flanges 20 and 38 on the lid and thebody portions 10 and 12, and the curled lip 46 of the flange 38 on thelid portion 10, make loading the lid portion 10 to the body portion 12quick and simple. Furthermore, the lid portion 10 and the body portion12 are self-centering with one another so that additional tooling is notnecessary to keep the components 10 and 12 centered during the weldingprocess.

When the sonitrode 32 is moved to the engaged position, the frictionsurface 34 contacts an outer surface 48 of the flange 38 on the lidportion 10. When the sonitrode 32 is in the engaged position, the flange38 on the lid portion 10 and the flange 20 on the body portion 12 areheld in contact with one another between the support surface 24 of thesupport assembly 22 and the friction surface 34 of the sonitrode 32, asbest shown in FIG. 3A.

An actuator 50 moves the sonitrode 32 between the engaged position andthe retracted position. The actuator 50 pushes the sonitrode 32 downwardsuch that when the sonitrode 32 is moved to the engaged position, thesonitrode 32 exerts a downward force to hold the flanges 20 and 38 ofthe lid and the body portions 10 and 12 of the metallic container 14 incontact with one another between the support surface 24 of the supportassembly 22 and the friction surface 34 of the sonitrode 32. When thesonitrode 32 is moved to the engaged position, the actuator 50 can movethe sonitrode 32 downward in stages such that the sonitrode 32 exerts aninitial downward force to hold flange 20 and 38 of the lid 10 and thebody 12 of the metallic container 14 in contact with one another betweenthe support surface 24 of the support assembly 22 and the frictionsurface 34 of the sonitrode 32, while the coating materials on thecontacting surfaces 42 and 44 are wiped out. Following the wipe out ofthe coating materials, the downward force can be increased to create thefriction weld between the materials forming the lid portion 10 and thebody portion 12 of the container 14. The actuator 50 is adapted toprovide a downward force between approximately 1300 N and approximately7200 N. Preferably, the downward force applied during the welding of thesurfaces 42 and 44 is approximately 2200 N.

A motor 52 is adapted to reciprocally rotate the sonitrode 32 relativeto the support assembly 22. Reciprocal movement of the sonitrode 32relative to the support assembly 22 moves the lid portion 10 relative tothe body portion 12. The motor 52 is adapted to reciprocally rotate thesonitrode 32 at a rate of between 15 KHz and 25 KHz. Preferably, thesonitrode 32 is reciprocally rotated at a frequency of approximately 20KHz. This reciprocal movement can create frictional wear necessary towipe out any protective coating on the surfaces 42 and 44, and cancreate the heat between the flanges 20, 38 of the lid portion 10 and thebody portion 12, such that a friction weld is formed between the flanges20, 38 of the lid portion 10 and the body portion 12 of the metalliccontainer 14.

Preferably, the sonitrode 32 is made from powered metal, and may betuned using sound waves to control the amplitude of the reciprocalrotation at the point of contact between the friction surface 34 and theflange 38 of the lid portion 10. The amplitude of the reciprocalrotation can be important and is dependant upon several factors,including, but not limited to, the diameter at the point of contactbetween the flange 38 of the lid portion 10 and the friction surface 34of the sonitrode 32, the magnitude of the downward force on thesonitrode 32, the thickness of the flanges 20, 38 of the lid portion 10and the body portion 12, etc. For example, the amplitude of reciprocalrotation for a typical carbonated beverage can would be on the scale ofapproximately 5×10⁻³ cm or about 0.1° of arc.

The sonitrode 32 is supported on a shaft 54 extending between the motor52 and the sonitrode 32. The shaft 54 has a cammed outer surface 56.Portions of the pivotally mounted clamshell anvil halves 30A, 30B engagethe cammed outer surface 56. Referring to FIGS. 1-3, each half 30A, 30Bof the clamshell anvil 30 includes a rolling contact 58. The supportassembly 22 includes springs 60 that bias the halves 30A, 30B of theclamshell anvil 30 away from the closed position and keeps the rollingcontacts 58 held against the cammed outer surface 56 of the shaft 54.When the sonitrode 32 is in the retracted position, the rolling contacts58 engage the shaft 54 at a narrow point in the shaft 54, wherein therolling contacts 58 can move inward and the springs 60 bias the halves30A, 30B of the clamshell anvil 30 to the open position, as shown inFIG. 1.

As the sonitrode 32 begins to move downward, as shown in FIG. 2, therolling contacts 58 follow the cammed outer surface 56 of the shaft 54and are pushed outward against the biasing springs 60 of the supportassembly 22. As the sonitrode 32 moves downward, the rolling contacts 58are contacting portions of the shaft 54 that are gradually increasing indiameter, such that the rolling contacts 58 are pushed outward, thehalves 30A, 30B of the clamshell anvil 30 are pivoted against thebiasing springs 60 and begin to pivot to the closed position.

Finally, as the sonitrode 32 and the shaft 54 continue to move downward,the rolling contacts 58 reach a point on the shaft 54 where the diameterof the shaft 54 pushes the rolling contacts 58 outward to a point wherethe halves 30A, 30B of the clamshell anvil 30 are pivoted to the closedposition, as shown in FIG. 3. The rolling contacts 58 reach the point onthe shaft 54 where the diameter of the shaft 54 pushes the rollingcontacts 58 outward such that the halves 30A, 30B of the clamshell anvil30 are pivoted to the closed position before the sonitrode 32 contactsthe lid portion 10 of the metallic container 14. Specifically, the twohalves 30A, 30B of the clamshell anvil 30 reach the closed position andthe support surface 24 contacts the outer surface 26 of the flange 20 onthe body portion 12 of the metallic container 14 prior to the frictionsurface 34 of the sonitrode 32 contacting the flange 38 on the lidportion 10 of the metallic container 14, thus resulting in some lostmotion.

This lost motion allows the sonitrode 32 to retract from the lid portion10 prior to the halves 30A, 30B of the clamshell anvil 30 opening.Referring to FIG. 3A, at least one of the clamshell anvil halves 30A,30B includes a stop 62 extending from an inner surface 64 of theclamshell anvil half 30A, 30B. The stop 62 is positioned verticallyabove the support surface 24, such that when the sonitrode 32 retractsfrom the lid portion 10 of the metallic container 14 after welding, ifthe lid portion 10 of the metallic container 14 sticks to the frictionsurface 34 of the sonitrode 32, the stop 62 will contact the lid portion10, thereby holding the metallic container 14 down as the sonitrode 32retracts upward.

If the halves 30A, 30B of the clamshell anvil 30 open immediately uponmotion of the sonitrode 32, then the halves 30A, 30B of the clamshellanvil 30 would pivot away from the metallic container 14, and themetallic container 14 could become stuck to the friction surface 34 ofthe sonitrode 32, requiring manual removal by an operator of theapparatus 16.

The risk of the lid portion 10 sticking to the friction surface 34 ofthe sonitrode 32 is a real concern, because in order for the frictionsurface 34 of the sonitrode 32 to grip the flange 38 on the lid portion10, the friction surface 34 of the sonitrode 32 is rough. In oneembodiment, the friction surface 34 of the sonitrode 32 has a knurledpattern formed therein. In order to assist in the removal of thesonitrode 32 from the lid portion 10 after welding, the knurled surfaceof the friction surface 34 can have a vertically oriented knurl 66formed therein, such as that shown in FIG. 11. Alternatively, a downwardpointing triangular shaped knurl pattern 68, such as the one shown inFIG. 10, can be used. These knurl patterns 66, 68, would more readilyallow the friction surface 34 of the sonitrode 32 to retract from thelid portion 10 with a reduced chance of the lid portion 10 sticking tothe friction surface 34.

Likewise, the support surface 24 of the support assembly 22 also has arough surface. This rough surface allows the support surface 24 to gripthe outer surface 26 of the flange 20 on the body portion 12 to preventsliding movement of the flange 20 of the body portion 12 relative to thesupport surface 24. As the support surface 24 retracts radially from theouter surface 26 of the body portion 12, the risk of the body portion 12sticking to the support surface 24 is not as important as with thesonitrode 32 and the lid portion 10, therefore a conventionalcriss-cross knurl pattern 70 can be used, such as that shown in FIG. 9.

The depth of the knurl patterns 66, 68, 70 on the friction surface 34 ofthe sonitrode 32 and the support surface 24 of the support assembly 22is calibrated according to the thickness of the flanges 20, 38 of thelid portion 10 and the body portion 12 and the downward pressure of thesonitrode 32. If the depth of the knurl pattern 66, 68, 70 is too deep,the downward pressure could push the knurl substantially or completelythrough the flanges 20, 38 of the lid portion 10 and the body portion12. Therefore, the thickness of the knurl is carefully calibrated toallow the knurl pattern to press into the flanges 20, 38 of the lidportion 10 and the body portion 12 sufficiently enough to engage andfrictionally grip the flanges 20, 38, without sinking deep enough intothe thickness of the flanges 20, 38 to compromise the structuralintegrity of the weld. Typically the depth of the knurl pattern 66, 68,70 is calibrated as a percentage of the thickness of the flanges 20, 38of the lid portion 10 and the body portion 12.

In another embodiment, the support surface 24 of the support assembly 22and the friction surface 34 of the sonitrode 32 have a textured surfacerather than a knurled surface. Referring to FIG. 12, the support surface24 of the support assembly 22 and the friction surface 34 of thesonitrode 32 can be sand-blasted or grit-blasted, thereby creating atextured surface 80. In still another embodiment, the support surface 24of the support assembly 22 and the friction surface 34 of the sonitrode32 can each include a raised ridge 82 extending thereabout. Referring toFIGS. 13 and 14, the raised ridge 82 extends around the support surface24 and the friction surface 34 in a serpentine manner. When the frictionsurface 34 of the sonitrode 32 contacts the lid portion 10 and theflanges 20, 38 of the lid portion 10 and the body portion 12 are heldbetween the friction surface 34 and the support surface 24, the raisedridges 82 on the friction surface 34 and support surface 24 will createpressure points against the flanges 20, 38. Other embodiments can beenvisioned wherein the support surface 24 of the support assembly 22 andthe friction surface 34 of the sonitrode 32 each include a raised ridge82 extending thereabout in a serpentine manner, and include portionsthat are grit blasted or sand blasted to increase the frictional grip ofthose portions.

Preferably, the interior surfaces 42, 44 of the lid portion 10 and thebody portion 12 are coated with a food compatible coating 72 prior tobeing assembled. These coatings 72 are typically organic coatings. Avariety of coatings can be used on the interior surfaces of the lidportion and the body portion of the container, which are preferablysatisfactory for food contact, to prevent corrosion of the inner surfaceof the metallic food container and to prevent the metal fromcontaminating the taste of the food placed therein. The coating can beany of the materials identified, for example, in U.S. Pat. No.5,739,215, which are hereby incorporated by reference. Typically, thebody portion and the lid portion have the inner surfaces coated prior tothe lid portion being attached to the body portion. It is important thatany process used to attach the lid portion 10 to the body portion 12does not compromise the integrity of any coatings 72 placed thereon.

The downward force that the sonitrode 32 places on the lid portion 10presses the flange 38 of the lid portion 10 and the flange 20 of thebody portion 12 together. That downward force and the frequency of thereciprocal movement of the sonitrode 32 are carefully calibrated suchthat the frictional heat generated from the reciprocal relative motionbetween the lid portion 10 and the body portion 12 is sufficient toinitially wipe out the coating between the lid portion 10 and the bodyportion 12 of the metallic container 14. Thereafter, the downward forceof the sonitrode 32 can be increased such that the frictional heatgenerated from the reciprocal relative motion between the lid portion 10and the body portion 12 creates a friction weld between the lid portion10 and the body portion 12 of the metallic container 14, while beingsufficiently low enough to prevent break-down of the coating 72 inwardlyadjacent to the weld area.

This allows the formation of a weld zone 74 between the inner surfaces42, 44 of the flanges 20, 38 of the lid portion 10 and the body portion12 while maintaining the integrity of the coating 72 on these surfaces42, 44. Referring to FIG. 6, a close up view shows the flange 38 of thelid portion 10 and the flange 20 of the body portion 12 prior towelding. The inner surface 42 of the flange 38 on the lid portion 10 hasa coating 72 placed thereon and the inner surface 44 of the flange 20 onthe body portion 12 has a coating 72 placed thereon. The coatings 72, aswell as protecting the contents of the metallic container 14, after thelid portion 10 is attached to the body portion 12, also assist in thefriction welding.

Thermoplastic coatings 72 can provide lubrication between the lidportion 10 and the body portion 12 to more easily allow relative motionbetween the two as the sonitrode 32 begins to move back and forth. Asthe frictional heat increases, the thermoplastic coatings 72 can becomemore fluid, thereby acting as a lubricant. After a short time, the heatbegins to build up, and the downward pressure of the sonitrode 32 pushesthe heated coating 72 away from the area directly between the frictionsurface 34 of the sonitrode 32 and the support surface 24 of the supportassembly 22, or specifically, the weld zone 74. In the embodimentincluding raised serpentine ridges 82 on the friction surface 34 and thesupport surface 24, the pressure points created by the raised ridges 82will push against the outer surfaces 26, 48 of the flanges 20, 38thereby defining flow paths between the inner surfaces 42, 44 of theflanges 20, 38. The liquefied coating material 72 will flow, via theflow paths, outward, away from the weld zone 74. In this way, the raisedserpentine ridges 82 assist in removing the coating material 72 frombetween the flanges 20, 38, thereby helping to insure a contaminant freeweld zone 74. Coatings 72 formed of thermoset resins are observed toquickly become powdered and expelled outward from the weld zone 74.

Referring to FIGS. 7 and 8, once the coatings 72 are wiped out from theweld zone 74, the flange 38 of the lid portion 10 and the flange 20 ofthe body portion 12 are in direct contact within the weld zone 74. Asreciprocal motion continues, the heat eventually builds up and forms afriction weld between the lid portion 10 and the body portion 12 withinthis weld zone 74. Referring specifically to FIG. 8, the weld zone 74 isthe area wherein the lid portion 10 and the body portion 12 are actuallywelded to one another. The coating material 72 that was wiped out of theweld zone 74 can form pockets 76 of coating material 72 immediatelyadjacent each side of the weld zone 74. These pockets 76 of coatingmaterial 72 helps insure that there are no gaps in the coating material72 at the point of welding.

Referring again to FIG. 3A, the friction surface 34 of the sonitrode 32and the support surface 24 of the support assembly 22 are oriented at anangle 40 relative to the longitudinal axis 36 of the apparatus, alongwhich the sonitrode 32 moves. Preferably, the friction surface 34 of thesonitrode 32 and the support surface 24 of the support assembly 22 areinwardly angled. The flanges 20, 38 on the lid portion 10 and the bodyportion 12 are correspondingly angled, as discussed previously. Theangled orientation means that the downward force of the sonitrode 32will provide a force to directly keep the flange 38 of the lid portion10 and the flange 20 of the body portion 12 held together. This forcewill also act to push downward on the lid portion 10 relative to thebody portion 12. This means that as the weld zone 74 is forming, thedownward force pushing on the lid portion 10 will cause the weld zone 74to smear radially inward. This increases the size of the weld zone 74and the depth of the weld between the lid portion 10 and the bodyportion 12.

The method of forming a metallic container 14 generally includes thesteps of providing a pre-formed body portion 12, providing a pre-formedlid portion 10, placing the lid portion 10 onto the body portion 12 andapplying a force to keep portions of the lid portion 10 and the bodyportion 12 held in contact with one another, and reciprocally rotatingthe lid portion 10 with respect to the body portion 12, therebygenerating frictional heat between the lid portion 10 and the bodyportion 12 such that a friction weld is formed therebetween.

Referring to FIGS. 4, 4A, 5, and 5A, preferably, the body portion 12 isgenerally cylindrically shaped and is open at one end, the open endhaving an angled flange 20 extending circumferentially around the openend. A coating 72 is placed on the inner surface 44 of the body portion12. The lid portion 10 is generally disk shaped and includes an angledflange 38 extending circumferentially around the disk perimeter. Theangle 40 of the flange 20 on the body portion 12 being approximatelyequal to the angle 40 of the flange 38 on the lid portion 10. The lidportion 10 has a coating 72 placed on the inner surface 42 as well.

Preferably, the lid portion 10 and the body portion 12 are cold formedfrom a metallic material such as aluminum. It is to be understood thatthe metallic container 14 can be made from any suitable metallicmaterial, and aluminum is being described here as one example of such ametallic material. The lid portion 10 is coated prior to the lid portion10 being cold formed into pre-formed shape, and the body portion 12 iscoated after being cold formed into the pre-formed shape.

The lid portion 10 and the body portion 12 are be placed together suchthat the inner surface 42 of the flange 38 of the lid portion 10contacts the inner surface 44 of the flange 20 on the body portion 12.The force applied to keep the inner surface 42 of the flange 38 on thelid portion 10 held in contact with the inner surface 44 of the flange20 on the body portion 12 should be between approximately 1800 N andapproximately 2700 N. Preferably, the force is approximately 2250 N.

The lid portion 10 is be rotated reciprocally relative to the bodyportion 12 at a rate between 15 KHz and 25 KHz. Preferably, the lidportion 10 is reciprocally rotated at a frequency of approximately 20KHz.

Preferably all steps are performed by providing an apparatus 16 such asthat described above. The body portion 12 of the metallic container 14,generally filled with suitable contents such as a food or beverage, isplaced onto the base 18 of the apparatus 16. The lid portion 10 of themetallic container 14 is then placed onto the body portion 12 of themetallic container 14.

The actuator 50 is activated and begins to move the sonitrode 32downward toward the metallic container 14. As the sonitrode 32 and theshaft 54 on which the sonitrode 32 is mounted, begin to move downward,the rolling contacts 58 on the two halves 30A, 30B of the clamshellanvil 30 follow the cammed outer surface 56 of the shaft 54, therebypushing the rolling contacts 58 outward and causing the two halves 30A,30B of the clamshell anvil 30 to pivot against the biasing springs 60mounted onto the support assembly 22.

When the rolling contacts 58 reach a point on the cammed outer surface56 of the shaft 54 wherein the two halves 30A, 30B of the clamshellanvil 30 are pivoted to the closed position, the support surface 24 ofthe clamshell anvil 30 contacts the outer surface 26 of the flange 20 onthe body portion 12 of the metallic container 14. The sonitrode 32continues to move downward to the engaged position, wherein the frictionsurface 34 of the sonitrode 32 contacts the flange 38 on the lid portion10 of the metallic container 14.

The actuator 50 pushes the sonitrode 32 downward with a force ofapproximately 2250 N. After the sonitrode 32 reaches the engagedposition, and the friction surface 34 of the sonitrode 32 is in contactwith the flange 38 of the lid portion 10 and the support surface 24 ofthe support assembly 22 is in contact with the flange 20 of the bodyportion 12, the motor 52 begins to reciprocally rotate the sonitrode 32.The sonitrode 32 reciprocally rotates relative to the support assembly22, thereby reciprocally rotating the lid portion 10 relative to thebody portion 12 of the metallic container 14. The motor 52 reciprocallyrotates the sonitrode 32 at a frequency of approximately 20 KHz, therebygenerating sufficient frictional heat to wipe out the coating 72 on theinner surfaces 42, 44 of the body portion 12 and the lid portion 10 tothe sides of the weld zone 74 and forming a friction weld between theflanges 20, 38 of the lid portion 10 and the body portion 12 within theweld zone.

Alternatively, the actuator 50 moves the sonitrode 32 to the engagedposition, and pushes the sonitrode 32 downward with a first downwardforce. The motor 52 is activated, and the sonitrode 32 is reciprocallyrotated at a first frequency for a first predetermined amount of time.Specifically, the sonitrode 32 exerts sufficient force (first downwardforce) and the motor 52 reciprocally rotates the sonitrode 32 at afrequency (first frequency) until any thermoplastic coating material 72placed on the inner surfaces 42, 44 of the flanges 20, 38 is allowed tomelt, and become liquid. The first downward force and the firstfrequency are sufficient to create frictional heat to melt the coatingmaterial 72, however not sufficient to create enough frictional heat toform a weld. This melted coating material 72 acts as a lubricant toallow continued movement between the flanges 20, 38.

However, the coating materials 72 could compromise the integrity of theweld formed between the flanges 20, 38, so the downward force and thefrequency of rotation are held at the first downward force and the firstfrequency until the melted thermoplastic coating material 72 hasmigrated away from the weld zone 74. It is possible, to use thefrictions surface 34 and support surface 24 illustrated in FIGS. 13 and14 to assist in this migration.

The support surface 24 and the friction surface 34 each have a raisedridge 82 extending therearound in a serpentine pattern such that whenthe friction surface 34 of the sonitrode 32 contacts the lid portion 10and the flanges 20, 38 of the lid portion 10 and the body portion 12 areheld between the friction surface 34 and the support surface 24, theraised ridges 82 on the friction surface 34 and support surface 24 willcreate pressure points against the flanges 20, 38. The first downwardpressure is adapted to apply sufficient pressure, such that the raisedserpentine ridges 82 on the friction surface 34 and the support surface24 create pressure points against the outer surfaces 26, 48 of theflanges 20, 38, thereby defining flow paths between the inner surfaces42, 44 of the flanges 20, 38. The flow paths will allow the meltedthermoplastic coating material 72 to more readily flow from within theweld zone 74, and the reciprocal rotation of the sonitrode 32 will helppush the melted thermoplastic coating material 72 through these flowpassages. Similar flow patterns are observed for powderednon-thermoplastic coatings.

Typically, when applied to a typical carbonated beverage can, it takesapproximately two to six hundredths of a second to wipe out the coatings72 from the weld zone 74. Once the coating material has been wiped out,the downward pressure of the sonitrode 32 is increased to a seconddownward force and the frequency of reciprocal rotation of the sonitrode32 is increased to second frequency. The downward pressure and thefrequency are increased to levels appropriate to create sufficient heatand pressure to form a friction weld between the flanges 20, 38, andheld at those levels until the friction weld is formed. When applied toa typical carbonated beverage can, this portion of the process takesapproximately one to two tenths of a second.

Preferably, the first downward force and the first frequency are betweenapproximately sixty percent and approximately seventy percent of thesecond downward force and the second frequency. As previously discussed,the downward force and the frequency are application dependant. Thedownward force and the frequency of reciprocal rotation, depend on thethickness of the flanges 20, 38, the material that is being welded, thediameter of the sonitrode 32, and other factors. For example, in aparticular application, the downward pressure and frequency ofreciprocal rotation necessary to create a friction weld between theflanges 20, 38 of the lid portion 10 and the body portion 12 are 2250 Nand 20 KHz, respectively. These are the second downward force and thesecond frequency. The first downward force and the first frequency wouldbe sixty to seventy percent of the second downward force and secondfrequency, or between 1350 N and 2200 N and between 12 and 14 KHz,respectively.

The method and apparatus 16 described above provide a technique ofattaching the lid portion 10 to the body portion 12 of a metalliccontainer 14 that creates a solid metal seal between the lid portion 10and the body portion 12, while maintaining the integrity of any coatings72 placed on the inner surfaces 42, 44 of either component. The processis quicker than any known prior processes, and eliminates additionalmaterial necessary for rolling the edges of the lid portion 10 and thebody portion 12 onto one another. Furthermore, no intermediate materialis necessary between the flanges 20, 38 of the lid portion 10 and thebody portion 12. The method and apparatus 16 described herein create aweld directly between the flanges 20, 38 of the lid portion 10 and thebody portion 12 with no intermediate material or gaskets of any kindnecessary. The temperatures of the process described above remainrelatively low compared to prior art processes, thereby making itpossible to maintain a food suitable coating 72 the inner surfaces 42,44 of the components.

In accordance with the provisions of the patent statutes, the presentinvention has been described in what is considered to represent itspreferred embodiment. However, it should be noted that the invention canbe practiced otherwise than as specifically illustrated and described.

1. A method of forming a metallic container comprising: providing apre-formed body portion being open at one end, the open end having anangled flange extending circumferentially therearound, and supportingthe pre-formed body portion on a support assembly; providing apre-formed lid portion having a shape sized to close the open end of thebody portion, said lid portion including an angled flange extendingcircumferentially therearound; contacting the lid portion with asonitrode that is movable with respect to the support assembly, movingthe sonitrode with the lid portion into an initial engagement with theopen end of the body portion so that an inner surface of the flange ofthe lid portion contacts an inner surface of the flange of the bodyportion and applying a first downward force to keep the flange innersurfaces of the lid portion and the body portion held in contact withone another; and reciprocally rotating the lid portion with respect tothe body portion at a first rate for a predetermined amount of time;increasing the downward force to a second downward force, larger thanthe first downward force, and continuing the rate of reciprocal rotationof the sonitrode to a rate that is at least as large as the first rateafter the predetermined amount of time has passed; and holding thesonitrode in the engaged position at the second downward force andmaintaining the reciprocal rotation of the sonitrode for a secondpredetermined amount of time, thereby generating frictional heat betweenthe inner surface of the flange of the lid portion and the inner surfaceof the flange of the body portion such that a metallic friction weld isformed therebetween.
 2. The method of claim 1, further comprising thesteps of: providing the pre-formed body portion with a generallycylindrically shape open at one end; and providing the pre-formed lidportion with a generally disk shape including the angled flangeextending circumferentially therearound, the angle of the flange on thebody portion being approximately equal to the angle of the flange on thelid portion.
 3. The method of claim 1, wherein said step of applying aforce to keep the flange inner surfaces of the lid portion and the bodyportion held in contact with one another includes applying a force ofbetween approximately 1800 N and 2700 N, and wherein said step ofreciprocally rotating the lid portion with respect to the body portionincludes reciprocally rotating the lid portion with respect to the bodyportion at a rate between 15 KHz and 25 KHz.
 4. A method of forming ametallic container comprising: providing a pre-formed body portion beingopen at one end, the open end having an angled flange extendingcircumferentially therearound, and supporting the pre-formed bodyportion on a support assembly; providing a pre-formed lid portion havinga shape sized to close the open end of the body portion, said lidportion including an angled flange extending circumferentiallytherearound; contacting the lid portion with a sonitrode that is movablewith respect to the support assembly, moving the sonitrode with the lidportion into an initial engagement with the open end of the body portionso that an inner surface of the flange of the lid portion contacts aninner surface of the flange of the body portion and applying a firstdownward force to keep the flange inner surfaces of the lid portion andthe body portion held in contact with one another; reciprocally rotatingthe lid portion with respect to the body portion at a first rate for apredetermined amount of time; continuing the downward force at a levelwhich is at least equal to the first downward force, and increasing therate of reciprocal rotation of the sonitrode to a second rate, higherthan the first rate, after the predetermined amount of time has passed;and holding the sonitrode in the engaged position at a level which is atleast equal to the first downward force and maintaining the reciprocalrotation of the sonitrode at the second rate for a second predeterminedamount of time, thereby generating frictional heat between the lidportion and the body portion such that a metallic friction weld isformed between the flange inner surfaces of the lid portion and the bodyportion.
 5. The method of claim 4, wherein the step of moving thesonitrode into an initial engagement a first downward force, such thatthe motor reciprocally rotates the sonitrode at a first rate for apredetermined amount of time includes the step of wiping out any coatingmaterial on the flange inner surfaces of the body portion and lidportion to expose a weld zone.
 6. A method of forming a metalliccontainer comprising: providing a pre-formed body portion at leastpartially coated with a coating; providing a pre-formed lid portion atleast partially coated with a coating; placing the lid portion onto thebody portion into an initial engagement; applying a downward force tokeep confronting coated portions of the lid portion and the body portionheld in contact with one another and reciprocally rotating the lidportion with respect to the body portion at a rate for a predeterminedamount of time, thereby generating a first frictional heat between saidconfronting portions of the lid portion and the body portion such thatthe coatings are wiped away from said confronting portions; andincreasing at least one of the downward force and the rate of reciprocalrotation after the predetermined amount of time has passed whilemaintaining the contact of the confronting portions of the lid and bodyportions for a second predetermined amount of time, thereby generating asecond frictional heat, larger than the first frictional heat, betweensaid confronting portions of the lid portion and the body portion suchthat a metallic friction weld is formed between said confrontingportions.
 7. The method of claim 6, further comprising the steps of:providing the pre-formed body portion with a generally cylindricallyshape open at one end, the open end having an angled flange extendingcircumferentially therearound being coated with said coating; andproviding the pre-formed lid portion with a generally disk shapeincluding an angled flange extending circumferentially therearound beingcoated with said coating, the angle of the flange on the body portionbeing approximately equal to the angle of the flange on the lid portion.8. The method of claim 7, wherein said placing and applying stepsinclude: placing the lid portion onto the body portion such that acoated inner surface of the flange of the lid portion contacts a coatedinner surface of the flange on the body portion; and applying the firstdownward force to keep the coated inner surface of the flange on the lidportion held in contact with the coated inner surface of the flange onthe body portion.
 9. The method of claim 6, wherein the placing stepincludes the step of supporting the pre-formed body portion on a supportassembly while contacting the lid portion with a sonitrode that ismovable with respect to the support assembly.
 10. The method of claim 9,wherein the applying and reciprocally rotating steps include applying adownward force with the sonitrode to keep confronting portions of thelid portion and the body portion held in contact with one another andreciprocally rotating the lid portion with respect to the body portionwith the sonitrode at a rate for a predetermined amount of time.
 11. Themethod of claim 10, wherein the increasing step includes increasing atleast one of the downward force and the rate of reciprocal rotation ofthe sonitrode after the predetermined amount of time has passed andholding the sonitrode in the engaged position for a second predeterminedamount of time.
 12. The method of claim 11, wherein said increasing stepincludes increasing the downward force to a larger downward force, andcontinuing the rate of reciprocal rotation of the sonitrode at least atsaid rate to generate said second frictional heat.
 13. The method ofclaim 11, wherein said increasing step includes increasing the rate ofreciprocal rotation of the sonitrode to a higher rate, and maintainingthe downward force of the sonitrode at least at said force to generatesaid second frictional heat.
 14. The method of claim 7, wherein saidstep of applying a downward force to keep confronting coated portions ofthe lid portion and the body portion held in contact with one anotherincludes applying a force of between approximately 1800 N and 2700 N.15. The method of claim 7, wherein said step of reciprocally rotatingthe lid portion with respect to the body portion at a rate includesreciprocally rotating the lid portion with respect to the body portionat a rate between 15 KHz and 25 KHz.